nan Rahila

Ionic liquid promoted spiroannulation via hetero-Michael addition and intramolecular heterocyclisation

A sequential efficient method for the synthesis of novel spiro-5-thiazolidin-2-one-indolo[1,5]benzothiazepine from readily available isatin, 4-thioxothiazolidin-2-one and 2-aminothiophenol is reported. The synthesis involves formation of N-methyl-3-(2-oxo-4-thioxothiazolidinon-5-ylidene)-1,3-dihydro indol-2-one by [bmIm]OH promoted Knoevenagel condensation of 4-thioxo-2-thiazolidinone with isatin. The Knoevenagel product on ionic liquid promoted thia-Michael addition with 2-aminothiophenol and intramolecular cyclocondensation yielded the title compounds with high atom economy. The ionic liquid, [bmIm]OH was recovered completely and recycled thrice for the synthesis with no appreciable decrease in the efficiency of the process. The whole sequence of reactions proceeded with quantitative transformation of reactants into spiro [1,5]benzothiazepine at ambient temperature. The sequential reaction pathway is supported by the isolation of the thia-Michael adduct of the knoevenagel product with 2-aminothiophenol and quantitative conversion of the adduct into the final products under the same reaction conditions.

Synthesis of fused pyridines in the presence of thiamine hydrochloride as an efficient and reusable catalyst in aqueous conditions

Efficient and straightforward synthesis of fused pyridine derivatives was achieved from electron-rich amino heterocycles and Knoevenagel products derived from aldehyde and malononitrile under aqueous media at 90 °C in the presence of thiamine hydrochloride as a reusable, green catalyst. The strategy in this protocol involves addition on an activated olefinic bond formed in situ by Knoevenagel condensation between an aromatic aldehyde and an active methylene compound. The Michael product on subsequent cyclo condensation yielded fused pyridine in high yield. It offers several advantages such as inexpensive, easily available and recyclable catalyst, simple operational procedure, excellent yield and use of aqueous medium that is considered to be relatively eco-friendly. Vitamin B1 was recovered and reused thrice.

Chitosan: an efficient promoter for the synthesis of 2-aminopyrimidine-5-carbonitrile derivatives in solvent free conditions

Reusable chitosan without any post-modification, with active –NH2 and –OH groups, was found to be a highly efficient and renewable heterogeneous catalyst for the rapid and convenient synthesis of 2-aminopyrimidine-5-carbonitrile derivatives from guanidines, aldehydes and cyanoketones, under mild reaction conditions at 85 °C in good yields. Undoubtedly this methodology gives a facile and straightforward pathway to construct 2-aminopyrimidine-5-carbonitrile derivatives in an eco-friendly fashion.

Molecular iodine catalysed domino cyclization in aqueous medium: a simple and efficient synthetic route to 1,4-dihydropyridazines

A facile, efficient and environmentally friendly approach has been developed for the diverse synthesis of 1,4-dihydropyridazines from (E)-2-benzylidene-1-phenylhydrazine and α,β-unsaturated aldehyde under aqueous condition using molecular iodine as a green and recoverable catalyst. This procedure features low cost and easily available starting materials, an inexpensive and recoverable catalyst, short reaction time, reliable scalability, excellent yield and mild reaction conditions, as well as use of aqueous medium. The scope of this method was thoroughly explored under three different reaction conditions resulting in the generation of a library of title compounds. In view of the various advantages of the present investigation, this methodology gives a convenient and straightforward pathway to construct 1,4-dihydropyridazines in an eco-friendly fashion.

Diastereoselective synthesis of furopyranopyridine in ionic liquid/water without additional catalyst

3,5-Diarylidene-1-methyl-piperidin-4-one derived in situ from N-methylpiperidinone and benzaldehyde undergoes intermolecular [4 + 2] hetero-Diels–Alder reactions with 2,3-dihydrofuran in [bmim]BF4–H2O (1 : 1) to afford furopyranopyridine derivatives in high to quantitative yields. Heterodienes, 3,5-diaryldiene-1-methylpiperidin-4-one an electron deficient oxadiene added to 2,3-dihydrofuran an electron rich dienophile because of an inverse electron demand, yielding furopyranopyridines with a high atom economy.

Sustainable construction: admicellar catalysed synthesis of pyrimido[4,5-b]quinolines in an aqueous system

A simple and highly efficient strategy has been documented for the rapid and convenient synthesis of 1-methyl-5-phenylbenzo[g]pyrimido[4,5-b]quinoline-2,4,6,11(1H,3H)-tetraone from aldehydes, 2-hydroxynaphthalene1,4dione and 6-aminouracil in the presence of nano ZnO under an aqueous admicellar system at 80 °C. Results show that nano ZnO is a potential catalyst for the synthesis of pyrimido[4,5-b]quinoline. Nano ZnO was recovered and reused efficiently several times for the synthesis of the desired product which is an essential parameter of green synthesis. The reported method represents an eco-friendly alternative to classical protocols. Nano size of ZnO was confirmed by EDS, transmission electron microscopy (TEM) and XRD techniques.

[bmim]OH promoted hydroalkynylation of nitrile and intramolecular hydroamination of the carbon–carbon multiple bond: an efficient and eco-compatible strategy for the synthesis of indolizinones

An efficient and novel hydroalkynylation of 2-cyanopyridine with arylacetylene and a subsequent intramolecular hydroamination promoted by a basic ionic-liquid, [bmim]OH, under microwave activation in the absence of an organic solvent and an inorganic base, yielding biodynamic indolizinones has been developed. The protocol involves [bmim]OH mediated in situ generation and addition of a nucleophilic alkynide from the aryl substituted terminal on a carbon alkyne of a polar nitrile group of 2-cyanopyridine. This results in the formation of a 2-pyridylphenylethynyl methimine intermediate which, on subsquent intramolecular nucleophilic addition of a pyridyl nitrogen on the carbon–carbon triple bond of the imine intermediate, heterocyclized into indolizinone with high atom economy. The reaction proceeded smoothly and quantitatively at an ambient temperature. The task specific [bmim]OH was recovered and reused three times without any appreciable decrease in its activity and product yield.

ZnO nanoparticle–β-cyclodextrin: a recyclable heterogeneous catalyst for the synthesis of 3-aryl-4H-benzo[1,4]thiazin-2-amine in water

A combination of ZnO nanoparticles and β-cyclodextrin was used as an efficient and green catalytic system for the synthesis of 3-aryl-4H-benzo[1,4]thiazin-2-amine via a one-pot, three-component reaction of an o-amino thiophenol, aromatic aldehydes and isocyanides in good to excellent yields at 60 °C in water. The nano size of ZnO was confirmed by transmission electron microscopy (TEM), XRD and UV-visible spectral techniques. A high catalytic activity and easy recovery and reuse for several cycles with consistent activity are additional eco-friendly attributes of this catalytic system.